At a typical refueling station or other refueling system, fuel is pumped from a storage tank to a vehicle fuel tank via a fuel dispenser. As the fuel enters the vehicle fuel tank, vapors from inside the vehicle tank are exhausted or forced out of the vehicle. Environmental laws and/or regulations typically require that the emitted vapors be captured. For example, stage II vacuum assist vapor recovery systems (i.e. vapor recovery systems utilized during vehicle refueling) may be required to capture/recover a certain percentage (such as 95%) of the vapor that is exhausted from the vehicle tank during refueling. The captured vapor is typically returned to the ullage space of the storage tank.
Vacuum assist vapor recovery system may utilize a vacuum source to aid in capturing the exhausted vapors. In some cases, the applied vacuum is regulated to vary in proportion to the rate of flow of dispensed fuel. However, many existing proportional vapor recovery valves provide insufficient internal sealing and ineffective proportional control.